Ignition Coil A Primary/Secondary Circuit Malfunction (Cylinder 1)
The P0351 code means the vehicle's onboard diagnostic system has detected: Ignition Coil A Primary/Secondary Circuit Malfunction (Cylinder 1). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- easy
- Estimated cost
- $50 - $300 for coil, spark plug, or wiring repair; $600 - $1,500+ in the rare case the PCM ignition-coil driver has failed and the module must be replaced (parts and labor)
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Common Symptoms
- Engine misfire on cylinder 1
- Rough idle and vibration
- Check Engine Light illuminated or flashing
- Reduced power and hesitation
- Strong exhaust smell from unburned fuel
Probable Causes (Ranked by Likelihood)
- Faulty ignition coil on cylinder 1 Very High
- Worn or fouled spark plug on cylinder 1 High
- Damaged coil connector or wiring High
- PCM coil driver circuit failure for cylinder 1 Moderate
- Short in coil-on-plug boot allowing spark leakage Low
Common Fixes by Vehicle
What techs usually find when diagnosing P0351 on specific vehicles — tap your vehicle for the fix and the exact part:
2009-2020 Ford F-150/Explorer 3.5L EcoBoost Easy DIY
Ignition coil 1 primary/secondary circuit malfunction. Check the coil connector for backed-out pins or corrosion. Measure coil primary resistance (0.3-1.0 ohm) and secondary resistance (5K-15K ohms). If out of spec, replace with an OE-quality Motorcraft unit. If resistance is normal, check the PCM driver circuit and the coil wiring for chafing near the intake manifold. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 20-30 min2010-2020 Chevrolet Silverado/GMC Sierra 5.3L Easy DIY
Coil 1 circuit fault. Check the ignition coil connector for corrosion or a loose fit. On the 5.3L, engine vibration can loosen coil connectors over time. Measure primary resistance (0.4-1.0 ohm). Replace with an OE-quality ACDelco unit if out of spec. Also check the coil driver circuit from the ECM. If the connector is corroded, repair the wiring and apply dielectric grease. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 15-20 min2009-2019 Dodge Ram/Chrysler 5.7L Hemi Easy DIY
Coil 1 primary/secondary circuit malfunction. The Hemi uses individual coil-on-plug ignition. Replace with an OE-quality Mopar unit. Check the connector for heat damage and corrosion. If the code returns after coil replacement, check the spark plug boot for carbon tracking which causes a short circuit. Also inspect the spark plug for cracking or fouling. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 15-20 minFrequently Asked Questions
Can I drive with code P0351?
You can drive short distances with a steady Check Engine Light. If the light is flashing, stop driving immediately as this indicates catalytic converter damage is occurring.
Is replacing an ignition coil a DIY repair?
Yes. On most vehicles with coil-on-plug ignition, replacing a coil is a simple DIY task requiring only basic tools. Unbolt the coil, disconnect the connector, and install the new one.
Should I replace the spark plug when replacing the coil?
Yes. A worn spark plug is often the root cause of coil failure. Always replace the spark plug along with the coil to prevent the new coil from being damaged by the old plug.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
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Swap cylinder 1 ignition coil with another cylinder -- if the misfire code moves, the coil is bad
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Inspect the spark plug on cylinder 1 for wear, fouling, or incorrect gap
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Measure coil primary resistance (0.4-2.0 ohms) and secondary resistance (6,000-15,000 ohms)
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Check the coil connector for melted plastic, corrosion, or loose pins
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Test the PCM coil driver signal at the connector with a noid light or oscilloscope
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- 2007-2017 Ford F-150
- 2008-2018 Toyota Camry
- 2005-2015 Honda Civic
- 2010-2020 Chevrolet Equinox
- 2009-2019 Hyundai Sonata
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